That guy is doing sloppy
inductive inference, and you're letting him get away with it by not calling him on his first, and foundational, errors. Ask for his sources of information, and examine each statement for sleight-of-hand. For example,
Sisifo wrote:Friend: Quantum physics postulates that anything possible that is not happening, happens in a different universe/reality.
I'm no quantum physicist, but I've been keeping tabs on it for a couple of decades now, and I've never read any such statement to the best of my memory. Sounds like something a fundie would say just to get his imaginary/fallacious ball rolling. Ask him where the fuck he came up with this assertion.
"...anything possible that is not happening, happens..."
Ahem. Wherever the fuck it happens it happens; doesn't matter if it's this universe/reality or any other. Self-contradiction.
This looks suspiciously like a 'wedge'. He's very subtly slipping in the assumption that there are other universes/realities (Did he make it sound like those were synonyms? They're not.), while quantum physics, which he pretends to be citing, is specifically limited to the
sub-microscopic realm. The greatest problem in physics at the moment is how to unite the physics of the very small with the physics of the very big. If they'd already done it, I think it would have been in the papers, don't you?
He's distracting you with the illusory authority of quantum physicists (as if they were even in consensus on the ultimate nature of things, which they clearly aren't) and helping you assume without examination that there are different universes/realities, so that he's free of the burden of providing support for this (hidden) assertion.
Me: As long as it is physically possible, agreed. It doesn't allow universes where physics laws are different. That's science fiction.
Friend: Agreed.
Well, no shit, he agreed. You just gave him his cookie, ie, that other universes/realities exist. Call him on it. Force him to admit that he's on pure speculation now, and tell him that speculation and 'tree fiddy' will get him a cup of coffee at Starbucks. In the end, he's jumping from SPECULATION, not necessary inference (which is what he's trying to disguise it as), to the assertion that he has proven something to be true.
Everything that followed just gradually drifted further and further away from anything based on empirical evidence, because you let him have his first cookie. 
"A philosopher is a blind man in a dark room looking for a black cat that isn't there. A theologian is the man who finds it." ~ H. L. Mencken
"We ain't a sharp species. We kill each other over arguments about what happens when you die, then fail to see the fucking irony in that."
"It is useless for the sheep to pass resolutions in favor of vegetarianism while the wolf remains of a different opinion."